Inductors are important components in many of the building blocks in wireless communication systems, such as RF bandpass filters, oscillators, impedance matching networks, emitter degeneration circuits, and/or baluns. Wireless communication standards place stringent requirements on performance and operating parameters, such as noise interference/immunity and power consumption. To accommodate the stringent requirements, high Q inductors are needed. One major obstacle in integrating communication ICs is the lack of high performance passive components, such as on-chip inductors.
Ideally, an inductor acts as a purely reactive device. However, in reality, the performance of an inductor is impacted by parasitic losses distributed within the inductor. FIG. 1 shows a model of a “real” inductor 100. The real inductor incurs losses, referred to as a “lossy inductor”. The losses can be due to, for example, built in resistance of the wire. The built in resistance 120 acts as though it were connected in series with the ideal inductor 110. Other losses can also include those due to, for example, skin effect, proximity effect, as well as eddy current in the underlying substrate. The losses incurred by the inductor are represented as Rs or effective series resistance. The total impedance Z of the circuit is defined as:Z=Rs+XL The total impedance includes a real component Rs and an imaginary component XL which is the effective reactance. The effective reactance of the inductor XL is equal to jωL. As such the total impedance Z of the inductor is defined as:Z=Rs+jωL 
The Q factor indicates how close a real inductor is to an ideal inductor. The higher the Q factor, the more pure is the inductor. Typically, a high Q factor is associated with a low signal loss. The Q factor is defined as follows:
  Q  =                    Im        ⁡                  (          Z          )                            Re        ⁡                  (          Z          )                      =                  ω        ⁢                                  ⁢        L                    R        s            In reality, Rs is large due to various parasitic effects, which leads to a low Q. To increase Q, active inductors have been proposed. However, such active inductors have peak Q at low frequencies and only over a narrow bandwidth. As such, conventional inductors are not applicable for high frequency or wide bandwidth applications.
Referring to FIG. 2, performance of a conventional inductor is shown. Line 210 plots the Q factor as a function of frequency while line 220 plots the inductance as a function of frequency. As shown, the conventional inductor has a peak Q 215 of about 6.9 at 8.5 GHz and a peak inductance 225 of 6.3 E-10 at about 12.9 GHz.
From the foregoing, it is desirable to provide high Q inductors which can be operated at high frequencies and/or over a broad frequency range.